1. Field of the Invention
This invention concerns a DUT board which is mounted on the test head of a semiconductor tester, as well as a device and a method for evaluating probe cards.
2. Discussion of the Related Art
There are various kinds of semiconductor testers, including semiconductor parametric testers, which measure the parametric properties of semiconductors formed on integrated circuits to IC testers which perform functional and performance tests of ICs. They perform 2 types of measurements: measurements in the wafer state, using a wafer prober, and measurements performed on packaged integrated circuits. When these measurements are performed, the wafer measurements and packaged integrated circuit measurements are performed by preparing a DUT board mounted on a test head for each DUT. Furthermore, the DUT boards used in the wafer measurements are called “probe cards.” As described, for example, in Japan Patent Publication No. 2001-228,173, a hole for confirming positions during probing is provided in the center of the card and probe needles for probing are placed on the periphery of this hole. As described in Japan Patent Publication No. 2001-228,173, in order to make contact with the plurality of contact pins placed on the test head, a plurality of contact terminals, that is, pads, are placed on the DUT board in positions which correspond to the arrangement of the contact pins. Conductive patterns are formed on the DUT board from these pads to the positions at which the parts, such as cables, ICs, and sockets, are placed, conforming to the DUT being tested.
Concerning the number of pads on this DUT board, in the case of the semiconductor parametric testers of the Agilent 4070 Series, for example, there are 48 channels, and 3 contact pins (a sense pin, force pin, and a guard pin are formed for each channel); therefore, 144 pads are provided. Furthermore, in the case of multi-channel IC testers, 500 to 1000 channels are formed, and the number of pads for these channels is quite large, even if only 1 contact pin is formed for each channel.
In quality evaluation tests of DUT boards, up to now, connection tests to investigate the connection relationships for each terminal and insulation resistance tests of the most critical parts, e.g., between terminals with narrow pattern gaps, were performed. The measurements were performed by using an insulation resistance meter, such as an Agilent 4339; the operator performed the measurements by hand, by using terminals such as banana plugs, which were put into contact with the pads of the blank board and the holes for mounting parts.
This kind of method, however, had various kinds of problems: the reproducibility of the measured values was poor, since the state of the connection was not constant, and the hand operation took considerable time, since several tens of measurements or more were made. Furthermore, when suspicious values were obtained the measurements were done over, so that in some cases contacts were made several times with each pad, causing abrasion of the pads. Furthermore, DUT boards in recent years required measurements of very small currents, on the fA (femtoampere, 10−15 ampere) order, and methods for measuring and evaluating the resistance performances of such DUT boards have been demanded which suppress errors due to current leaks and have good reproducibilities.